The present disclosure relates to a power supply system, an image forming apparatus having the power supply system, and a low-capacity AC processing circuit, and particularly, to a technology for suppressing a surge voltage which enters a power supply.
As an example of technologies for suppressing a surge voltage entering a power supply according to the related art, a constant voltage component is connected in parallel to a common-mode inductor, also called a common-mode choke coil, of a power input filter unit, thereby absorbing a counter-electromotive force which the power input filter unit generates in response to input of a surge voltage attributable to induced lightening or the like. This constant voltage component is provided to prevent damages of insulating components such as a transformer of a switching power supply and a photocoupler.